Posted by Mary Ellin D'Agostino
Ok, so you have rolled and rolled and rolled and just can't get that perfectly sized, even, and smooth slab to create your masterpiece in metal clay. Cracks, seams, thicker in the middle, raggedy edges...
What is the problem? Aaarrrggghhh!
Whether you are a beginner or a pro, there are a few things to keep in mind when trying to roll your clay out into the perfect slab.
If you are consistently getting a reasonably good center to your rolled slab, but the edges are raggedy, one simple solution is to start with a larger ball or slug (a cylindrical fat pre-form) of clay and trim the slab to the desired shape and size after rolling. This is not the perfect solution, but if it gets you what you want, it is good enough. Of course, this only works if you have extra clay.
The Un-seamed Ball
If you have problems with visible lines in the clay or a ragged edge, it is often due to not having a good pre-form of clay. If you have a freshly opened pat of metal clay you can just roll it out. More often, when working with clay we need to roll it into a ball or a slug that will then be rolled flat into a slab or round into a coil/snake. If there are seams in the clay ball or slug, they often interfere with creating that smooth, consistent slab.
To form a consistent ball without seams, you need to roll it between your lightly greased palms while applying pressure. It doesn't have to be perfectly round. The key is to press all the seams, lines, and imperfections outforcing the clay to join to itself.
This is an absolutely fundamental skill to perfect for the metal clay artisan.A good pre-form will create a good slab or coil.
Too wet, too dry, too greasy...? Another key is to have clay of the proper consistency. Aim for the consistency of silver clay right out of the package. It should be pliable, stick to itself easily, but not to your lightly greased hands. I will write a post on clay consistency problems and solutions later.
Slats, Cards, and Spacers
The next key is to have good spacing tools. There are scads of spacing tools out there. It seems like every company and teacher has a different solution for this essential slab rolling tool. Almost all of the ones being sold commercially will work, but each solution has its pros and cons.
The key is that you have at least two consistent and matching spacers in the thickness you want your slab to be and two a little thicker than you want it to be. A full range of sizes is great!
Stacking up poker playing cards is an easy and cheap solution (just use that deck that is missing the 3 of clubs). You can tape or glue the cards together to create more stable stacks. I like to use popsicle sticks and wooden coffee stirrers they come in a range of sizes and you can buy them if you need a lot or just grab a couple at the local coffee shop (buy something so you compensate the shop!).
Place the thicker-than-you-want slats on your work surface on either side of the clay pre-form and use your roller to roll out the clay. You may need to flatten the pre-form a little before rolling. The slats will help you roll the clay to a smooth, even thickness (more on this later). Pick up the clay and lay it on your (greased!) texture and re-roll using the slats that are the thickness you want. The key here is that the pre-rolled slab will be less prone to getting stuck into/onto many textures (cloth, paper, & rubber stamps) than if you just roll from ball to slab directly on the texture.
You often don't want a perfectly round pre-form. When rolled out, the round ball becomes an oval. If you want it to roll out round, you actually want to start
with an ovoid or cylindrical form. Perfectly round is difficult to achieve when just rolling out the clay. Circle cutters or templates are your friends.
The easiest way to get a truly round slab is to roll it larger and then use a circle cutter or template. Another way is to start with a round ball, place it on your work surface (or between sheets of plastic) with the slats or cards around it and use a Plexiglas snake roller (or other smooth, flat, rigid object) to press directly downward.
Metal Clay Memory
Ever notice that it always ends up thicker in the middle? It is especially vexing if you are trying to create a large slab that is a consistent thickness.
Why does it do that? Aaarrrggghhh!
Believe it or not, the cause is the same reason it is sometimes difficult to create that un-seamed pre-form. Metal, clay, and metal clay have memories. Yep, no brain, no mind, but they do have material memories. Like plastic or rubber, metal clays want to go back to the last stable shape or position they were in, so you have to convince them that a new position or shape is where they want to be.
Ever roll out dough for a pie shell? That stuff really springs back after rolling. You have to roll it, rotate it, roll it again, rotate it, roll it again.... until you get it to remain in the size, shape, and thickness desired. Happily, metal clay isn't quite so elastic, but you will get a more consistent slab if you roll the slab along one axis, then rotate the slats and clay 90° and roll again. It can also help to start rolling from the center outward in one direction, then return to center and roll in the other direction rather than rolling from one end to the other.
If you are having trouble with the clay sticking to a rigid work surface or if you are creating an especially thin slab, you might want to work between flexible work surface sheets (Teflon, cut up plastic bags, or sheet protectors). A flexible work surface can really help you get the clay off when it is time to move it. Otherwise, let it dry completely and it should slip off your work surface. If you find that the clay is warping as it dries (especially if you are drying with heat), you can try letting the clay dry naturally in the open air or place it on a permeable surface such as a paper towel or piece of cloth so it can dry on both sides evenly.
Another cause of warping and unevenness can be picking up the clay. When you lift up the clay and peel it off of the work surface, you actually stretch it, so if you are trying to create precision pieces like matching earrings, you don't want to pick it up after the final roll. Instead, let it dry flat on the work surface.
But how do I dry it on a permeable surface, work it on a smooth (non-porous) surface, and get it to dry without warping? Aaarrrggghhh!
This is a problem. If anyone has found a permeable, non-sticking, flat work surface, please let all of us know what it is!
In life and art there are seldom perfect solutions for things and this is one of those situations. If your piece is reasonably thick and not too large, just let it dry on the work surface before moving it. If the piece is very thin and large, you may opt to do the final rolling on cloth (greased sheer synthetic cloth with an even and fine weave works better than natural fiber cloth) or between cloth and your texture surface. When you pick it up on the cloth, the whole thing can be placed in/on your drying device. If you are using a flat heated surface, you may want to put a screen or a few layers of cloth or paper towels under the piece to ensure air circulation. If you can't live with a cloth texture, roll the slab slightly thicker than desired and sand it after drying.
To minimize warping, drying without heat is better than with heat. If the piece is still warped after drying and appears to be otherwise acceptable, you can moisten it slightly, place it between layers of cloth or paper towels with a weight on top of it and re-dry it. I will write more on the warping issue later.
And I thought this would be a short post! I am sure there is more to say on this subject and look forward to additional comments, suggestions, and insights!